So I recently installed Sirius radio plug and play kits in two cars, both done the same way, and both have the same problem. Both are aftermarket head units with RCA inputs. The Sirius is powered via a new accessory outlet in each car (still wanted to retain use of factory outlets). There is interference that corresponds to engine RPM. I've been reading up on the issue and have determined it's either in the RCA connections or the power/ground at the outlets. I tried a ground loop isolator I had laying around on the RCA cables and it simply drained much of the sound. I plan to throw one in my Trans Am soon, and would like to make sure I have it down before I do. How should I test to see which is my problem and how should I fix it? Thanks in advance.

 

you need to ground the sirius's -wire to the same spot as the head unit. if you have subs, i would ground the head unit and sirius reciever at the same spot as the amp ground cable to chassis point. the noise is alternator feedback, i doubt its in the rca's. sounds like a power circuit ground loop.

 

Ok, so the ground wire for the Sirius (i.e. the accessory outlet) should be at the same spot as the head unit, is that correct? I figured it was alternator feedback as well, just wasn't sure if it was somehow affecting the RCA being that they aren't heavily shielded.

 

i would personally cut the cigar lighter adapter off the sirius harness and just wire it to the radio, but if it has a built in convertor in the adapetr it will be a little different.
but basically, wire the sirius to turn on with the radio, and it should eleminate the noise.
oh and do you have subs andd amp?

 

I just went outside and hooked up the acc. outlet ground to the head unit's ground and the noise is practically non-existent and does not change with regards to RPM. I was originally going to hard wire the Sirius, but it has a built in 12V -> 5V circuit, so I just wired in a new outlet ($3) to tuck it away. The car I just fixed has no subs and no amp. The other car has a factory amp, and the Trans Am will be getting an amp to power two additional speakers. Basically, would you suggest grounding ALL audio equipment to the same point?

 

factory amp should be fine, but generaly speaking common ground is the best way. glad its solved.

 

Thanks for the help.

 

Alright, in one of the cars (the one with the factory amp) the interference came back - it's not nearly as bad as it initially was, but it is very noticeable. Any ideas?

 

donno, try grounding the radio/sat receiver at the factory amps ground location.